1. Field of the Invention
This invention pertains to an improved system and method of cleansing a filter bed. In particular, this invention relates to automatic backwash filtering systems. More in particular, this invention directs itself to an improved system for cleansing a filter bed utilizing two separate and distinct operations including a backwashing cycle and a purging cycle. Further, this invention pertains to an automatic backwashing filter system which permits substantial utilization of the same fluid flow elements in both a backwashing operation and a purging operation.
2. Prior Art
Automatic backwash filter systems are known in the art as exemplified in U.S. Pat. Nos. 3,239,061 and 4,133,766 assigned to the assignee corporation of this invention concept. However, such automatic backwash filters provide for a singular backwashing operation of the filter beds. It has been found in such prior art systems that there is a possibility that particulate solid contaminants or organisms have been found at the bottom of the filter media bed subsequent to the backwashing operation. In such prior art systems there is a possibility that the particulate material may pass through the filter underdrain and contaminate the filtrate.
Such prior art systems do not purge the filter bed subsequent to the backwashing operation cycle for removal of further contaminants from the filter bed. Thus, in such prior art filtering systems, the safety factor does not provide for a maximization of the filtering of the overall filtering system.
Additionally, where it would be necessary to insert a purge cycle into the prior art filtering systems, such would be complicated by additional hardware and pumping consideration mechanisms which would greatly increase the cost of such prior art systems. Further, the additional hardware and pumping elements would increase the volume considerations of such filtering systems.